Robotic transanal minimally invasive surgery (R-TAMIS): current evidence in the treatment of early rectal neoplasia

Introduction Robotic transanal minimally invasive surgery (R-TAMIS) was introduced in 2012 for the excision of benign rectal polyps and low grade rectal cancer. Ergonomic improvements over traditional laparoscopic TAMIS (L-TAMIS) include increased dexterity within a small operative field, with possibility of better surgical precision. We aim to collate the existing data surrounding the use of R-TAMIS to treat rectal neoplasms from cohort studies and larger case series, providing a foundation for future, large-scale, comparative studies. Methods Medline, EMBASE and Web of Science were searched as part of our review. Randomised controlled trials (RCTs), cohort studies or large case series (≥ 5 patients) investigating the use of R-TAMIS to resect rectal neoplasia (benign or malignant) were eligible for inclusion in our analysis. Quality assessment of included studies was performed via the Newcastle Ottawa Scale (NOS) risk of bias tool. Outcomes extracted included basic participant characteristics, operative details and histopathological/oncological outcomes. Results Eighteen studies on 317 participants were included in our analysis. The quality of studies was generally satisfactory. Overall complication rate from R-TAMIS was 9.7%. Clear margins (R0) were reported in 96.2% of patients. Local recurrence (benign or malignant) occurred in 2.2% of patients during the specified follow-up periods. Conclusion Our review highlights the current evidence for R-TAMIS in the local excision of rectal lesions. While R-TAMIS appears to have complication, margin negativity and recurrence rates superior to those of published L-TAMIS series, comparative studies are needed. Supplementary Information The online version contains supplementary material available at 10.1007/s00384-024-04645-4.


Introduction
Robotic transanal minimally invasive surgery (R-TAMIS) was introduced in 2012 for the excision of benign rectal polyps and low grade rectal cancer [1].Robotic platforms offer the benefits of wristed articulation, 3D optics and improved ergonomics, combatting issues posed by traditional laparoscopic TAMIS (L-TAMIS) [2,3].Theoretical benefits of R-TAMIS include superior oncologic resections and increased dexterity, via fine motion scaling and articulated instruments respectively [4].Similarly, the use of a robotic platform averts the need of an active surgical assistant in the already confined work space [5].
Despite promising reports in the literature, there is a void of large comparative studies, particularly comparing perioperative and oncological outcomes between R-TAMIS and L-TAMIS [5].In addition, most of the current literature on

Search strategy
The following databases were searched as part of the systematic review in October 2023: Medline, EMBASE and Web of Science.The terms included (R-TAMIS OR TAMIS OR Transanal OR Trans-anal) AND (Rect*).The last date of search was 1st of October 2023.The grey literature was also searched to further identify other suitable publications.

Inclusion criteria
The studies were assessed for eligibility based on the following inclusion criteria.Randomised controlled trials (RCTs), cohort studies or large case series (≥ 5 patients) investigating the use of R-TAMIS to resect rectal neoplasia (benign or malignant) were eligible for inclusion in our analysis.

Study selection, data extraction and critical appraisal
A database was created using the reference managing software EndNote X9™.Two researchers (NOS and HCT) reviewed outputs from the searches independently of each other.
Initially, duplicates were removed.The study titles were then screened and assessed for potential relevance.The abstracts of selected potential studies were then read and assessed for eligibility for inclusion, based on the inclusion/ exclusion criteria detailed above.The rejected studies were grouped together in the database by their reason for exclusion.The full texts of the abstracts deemed eligible for inclusion were then further analysed using the same criteria.
In order to extract and store data efficiently, the Cochrane Collaboration screening and data extraction tool, Covidence, was used [14].Data was collected by two reviewers (NOS and HCT) independently, using the following headings: study details, study design, population, intervention, comparison groups and outcomes.Conf licts between the two reviewers were resolved following an open discussion and a final decision by the senior author (MK).
Assessment of potential biases for the non-RCT studies was assessed using the Newcastle-Ottawa scale (NOS) risk of bias tool, and the results were tabulated.This assessment tool grades each study as being 'satisfactory' or 'unsatisfactory' across various categories.We assigned stars to evaluate study quality: 7 stars, 'very good'; 5-6 stars, 'good'; 3-4 stars, 'satisfactory'; and 0-2 stars, 'unsatisfactory'.The critical appraisal was completed by two reviewers independently (NOS and HCT), where once again a third reviewer (MK) was asked to arbitrate in cases of discrepancies in opinion.

Systematic review registration
Our systematic review was registered on PROSPERO in October 2023 (470657).

Search results
The literature search described above yielded a total of 782 results (Supplementary Material S1).Following the removal of 163 duplicates, 619 studies were screened.After the initial screening, 53 abstracts were reviewed and assessed for eligibility, of which 30 were selected for full-text review.From these 30 full texts, a total of 18 studies met the inclusion criteria and were included in our analysis.
In regards to quality assessment, seven studies were 'very good', nine studies were 'good', two studies were 'satisfactory' and zero studies were 'unsatisfactory' when scored using the Newcastle-Ottawa Scale risk of bias tool.Supplementary Material S2 summarises the results of our risk of bias assessment.

Participant characteristics
The total number of participants from the 18 included studies was 317.The median follow-up across studies was 30 months (range 12-63).Basic participant characteristics are presented in Table 2. Indications for R-TAMIS included resection of benign neoplasia, early malignant lesions, lesions unresectable by endoscopy and select T2/ T3 lesions in patients unfit for or unwilling to proceed with radical surgery.

Operative details
DaVinci robotic platforms (S, Si, SP or Xi) were used in all but two of the included studies reporting platform models [1, 5, 11, 15-20, 22-25, 27-29].Fok et al. utilised the Medrobotics Flex Robotic System on their cohort, whereas Paull et al. compared outcomes between the DaVinci Si and Medrobotics Flex Robotic System in their respective studies on R-TAMIS [21,26].Patient positioning throughout studies included lithotomy, modified lithotomy, prone jackknife and hockey-stick decubitus.Variable positions within individual studies were attributed to surgeon preference or tumour location (anterior, posterior, lateral).Fifteen studies reported using the Applied Medical GelPOINT Path Transanal Access Platform.Hompes et al. use a transanal glove port, generally considered a safe, inexpensive and readily available alternative tool in transanal surgery [22].Operative details are demonstrated in Table 3.The overall mean operative time across the included studies was calculated as 110 +/− 22 min.

Histopathological and oncological data
Tumour specifications were similar across the included studies.Specimen fragmentation occurred in only four cases.The pooled margin positivity rate across studies was 3.8% (n = 11/286).Out of the reported, the overall local recurrence (benign or malignant) occurred in 2.2% (n = 5/232) of patients within the specified follow-up period.The recurrence locations included the proctectomy scar site, anorectal junction and surgical bed.The histopathological and oncological data is demonstrated in Table 5.

Cost
Only two of the studies included in our analysis reported costs associated with R-TAMIS [5,22].Lee et al. reported direct costs of $3562 and $4440.92 of L-TAMIS and R-TAMIS respectively in their comparative study [5].Hompes et al. reported a far more economical cost of €837 for a single R-TAMIS case in their institute [22].Neither study incorporated the capital costs of robotic platforms in their calculations.

Discussion
Transanal minimally invasive local excision remains an acceptable treatment option for early-stage rectal tumours (T1, N0) within 3-8 cm of the anal verge in the absence of nodal involvement on local staging [30].While this procedure has traditionally been performed laparoscopically, recent evidence has suggested R-TAMIS as a safe alternative, with better articulation and superior visualisation [24].We sought to synthesise currently available data on R-TAMIS, to assess its safety and efficacy profile on cases to date.
Our review was comprised of 317 patients from 18 cohort studies or large case series (≥ 5 patients) highlighting practical aspects of R-TAMIS in addition to peri-operative and oncological outcomes.Overall complication rate from R-TAMIS was 9.7%.Clear margins (R0) were reported in 96.2% of patients.Local recurrence occurred in 2.2% of patients during the specified follow-up periods.A recent systematic review of laparoscopic TAMIS outcomes in over 1200 cases by Kim et al. found an overall complication rate of 18.4% (n = 222/1205) [31].Margin positivity rates were also elevated at 8.6% (n = 101/1173).Finally, local recurrence was reported as 7.2% (n = 54/746).While these findings suggest a potential benefit of R-TAMIS, these studies were observational and non-comparative, making side-byside comparison difficult and unreliable.
To date, only one study has been published directly comparing outcomes between the laparoscopic and roboticassisted approach in patients undergoing transanal local excision of rectal lesions.In their single-centre review of 40 consecutive patients, Lee et al. compared the two approaches in terms of peri-operative outcomes, histopathological outcomes and cost [5].Their review found no significant difference between L-TAMIS and R-TAMIS in any outcome other than cost, which was significantly higher in the R-TAMIS group (median direct cost $3562 vs. $4440.92).A breakdown of cost was not provided in this study.
Our study has several limitations.Despite only including cohort studies or large case series, the majority of included studies contained small numbers of participants, which are by default highly susceptible to potential selection bias.Similarly, a lack of comparative studies made metaanalysis of results and a statistical comparison between surgical approaches not feasible.Further studies on larger populations, ideally in the form of randomised control trials or matched cohorts, are required before conclusions can be drawn on the superiority of one modality over another.Nevertheless, R-TAMIS appears to be a safe and feasible alternative to L-TAMIS, in the transanal local excision of rectal tumours.

Conclusion
Our review highlights the current evidence for R-TAMIS in the local excision of rectal lesions.While R-TAMIS appears to have complication, margin negativity and recurrence rates superior to those of L-TAMIS published elsewhere in the literature, accurate conclusions cannot be drawn in the absence of comparative studies.Future research focusing on comparing these two approaches will shed light on best practices.

Table 1
Methodological characteristics of the included studies

Table 3
Operative details

Table 4
Peri-operative details

Table 5
Histopathological and oncological data